Apparatus and method for rapid charging using shared power electronics

ABSTRACT

An apparatus comprises a power electronic energy conversion system comprising a first energy storage device configured to store DC energy and a first voltage converter configured to convert a second voltage from a remote power supply into a first charging voltage configured to charge the first energy storage device. The apparatus also includes a first controller configured to control the first voltage converter to convert the second voltage into the first charging voltage and to provide the first charging voltage to the first energy storage device during a charging mode of operation and communicate with a second controller located remotely from the power electronic energy conversion system to cause a second charging voltage to be provided to the first energy storage device during the charging mode of operation to rapidly charge the first energy storage device.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent Ser. No.14/219,201, filed Mar. 19, 2014, which is a continuation of, and claimspriority to, U.S. patent application Ser. No. 12/641,359, filed Dec. 18,2009, now U.S. Pat. No. 8,698,451, issued Apr. 15, 2014, the disclosuresof which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Embodiments of the invention relate generally to electric drive systemsincluding hybrid and electric vehicles and, more particularly, torapidly charging one electric drive system using shared powerelectronics of one or more additional electric drive systems.

Hybrid electric vehicles may combine an internal combustion engine andan electric motor powered by an energy storage device, such as atraction battery, to propel the vehicle. Such a combination may increaseoverall fuel efficiency by enabling the combustion engine and theelectric motor to each operate in respective ranges of increasedefficiency. Electric motors, for example, may be efficient ataccelerating from a standing start, while combustion engines may beefficient during sustained periods of constant engine operation, such asin highway driving. Having an electric motor to boost initialacceleration allows combustion engines in hybrid vehicles to be smallerand more fuel efficient.

Purely electric vehicles use stored electrical energy to power anelectric motor, which propels the vehicle and may also operate auxiliarydrives. Purely electric vehicles may use one or more sources of storedelectrical energy. For example, a first source of stored electricalenergy may be used to provide longer-lasting energy while a secondsource of stored electrical energy may be used to provide higher-powerenergy for, for example, acceleration.

Plug-in electric vehicles, whether of the hybrid electric type or of thepurely electric type, are configured to use electrical energy from anexternal source to recharge the traction battery. Such vehicles mayinclude on-road and off-road vehicles, golf cars, neighborhood electricvehicles, forklifts, and utility trucks as examples. These vehicles mayuse either off-board stationary battery chargers, on-board batterychargers, or a combination of off-board stationary battery chargers andon-board battery chargers to transfer electrical energy from a utilitygrid or renewable energy source to the vehicle's on-board tractionbattery. Plug-in vehicles may include circuitry and connections tofacilitate the recharging of the traction battery from the utility gridor other external source, for example. The battery charging circuitry,however, may include dedicated components such as boost converters,high-frequency filters, choppers, inductors, and other electricalcomponents dedicated only to transferring energy between the on-boardelectrical storage device and the external source. These additionaldedicated components add extra cost and weight to the vehicle.

In addition, the total current available for recharging the on-boardelectrical storage device using only the on-board battery chargingcircuitry of the vehicle is limited to the total current that theon-board battery charging circuitry can supply. The on-board electricalstorage device, however, may be designed to accept a charging currentmuch greater than the total current supplied by the on-board batterycharging circuitry. Increasing the total current supplied by theon-board battery charging circuitry typically includes increasing thesize and capacity of the circuitry components, which adds yet additionalcost and weight to the vehicle.

It would therefore be desirable to provide an apparatus to facilitatethe transfer of electrical energy from multiple external sources to theon-board electrical storage device of a plug-in vehicle that reduces thenumber of components dedicated only to transferring energy between theon-board electrical storage device and the external source and thatincreases the total current available for charging the on-boardelectrical storage device.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the invention, an apparatus comprises a powerelectronic energy conversion system comprising a first energy storagedevice configured to store DC energy and a first voltage converterconfigured to convert a stored voltage from the first energy storagedevice into a first voltage configured to drive an electromechanicaldevice. The first voltage converter is also configured to convert asecond voltage from a remote power supply into a first charging voltageconfigured to charge the first energy storage device. The apparatus alsoincludes a first controller configured to control the first voltageconverter to convert the second voltage into the first charging voltageand to provide the first charging voltage to the first energy storagedevice during a charging mode of operation and communicate with a secondcontroller located remotely from the power electronic energy conversionsystem to cause a second charging voltage to be provided to the firstenergy storage device during the charging mode of operation to rapidlycharge the first energy storage device.

In accordance with another aspect of the invention, a method comprisescoupling a first energy storage device to a first voltage converter,wherein the first energy storage device is configured to storeelectrical energy and wherein the first voltage converter is configuredto convert a stored voltage from the first energy storage device into afirst voltage configured to drive a motor and to convert a secondvoltage from a first remote power supply into a first charging voltageconfigured to charge the first energy storage device. The method alsocomprises coupling a first controller to the first voltage converter andconfiguring the first controller to cause the first voltage converter toconvert the second voltage into the first charging voltage and toprovide the first charging voltage to the first energy storage deviceduring a rapid charging mode of operation. The method further comprisesconfiguring the first controller to cause a second charging voltage froma second remote power supply to be provided to the first energy storagedevice during the rapid charging mode of operation to rapidly charge thefirst energy storage device.

In accordance with yet another aspect of the invention, a systemcomprises a first power bus, a second power bus, and a first vehicle.The first vehicle comprises a first energy storage device configured tostore DC energy, a first motor and a first voltage converter configuredto convert a stored voltage from the first energy storage device into amotoring voltage configured to drive the first motor and to convert afirst voltage from the first power bus into a first charging voltageconfigured to charge the first energy storage device. The first vehiclealso comprises a first controller configured to control the firstvoltage converter to convert the first voltage into the first chargingvoltage and to provide the first charging voltage to the first energystorage device. The system also comprises a first energy conversionsystem located remotely from the first vehicle and comprising a secondvoltage converter configured to convert the first voltage from the firstpower bus into a second charging voltage configured to charge the firstenergy storage device of the first vehicle. The first energy conversionsystem further comprises a second controller configured to control thesecond voltage converter to convert the first voltage into the secondcharging voltage and to provide the second charging voltage to thesecond power bus and communicate with the first controller to cause thesecond charging voltage to be provided from the second power bus to thefirst energy storage device to rapidly charge the first energy storagedevice.

Various other features and advantages will be made apparent from thefollowing detailed description and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate embodiments presently contemplated for carryingout the invention.

In the drawings:

FIG. 1 is a schematic block diagram of a charging system according to anembodiment of the invention.

FIG. 2 is a schematic diagram of a portion of the charging system ofFIG. 1 according to an embodiment of the invention.

FIG. 3 is a schematic diagram of the charging system shown in FIG. 2according to another embodiment of the invention.

FIG. 4 is a schematic diagram of another a portion of the chargingsystem of FIG. 1 according to an embodiment of the invention.

FIG. 5 is a schematic diagram of another a portion of the chargingsystem of FIG. 1 according to an embodiment of the invention.

FIG. 6 is a schematic diagram of another a portion of the chargingsystem of FIG. 1 according to an embodiment of the invention.

FIG. 7 is a schematic diagram of another a portion of the chargingsystem of FIG. 1 according to an embodiment of the invention.

FIG. 8 is a schematic diagram of the charging unit of FIG. 7 accordingto an embodiment of the invention.

FIG. 9 is a schematic diagram of the charging unit of FIG. 7 accordingto an embodiment of the invention.

FIG. 10 is a schematic diagram of another a portion of the chargingsystem of FIG. 1 according to an embodiment of the invention.

DETAILED DESCRIPTION

FIG. 1 is a schematic block diagram of the infrastructure of a chargingsystem 2 according to an embodiment of the invention. Charging system 2illustrates a plurality of vehicles 4, 6, 8 coupled to a respectivecharging bay or socket 10, 12, 14 of a charging station 16. Chargingsystem 2 may include, in one embodiment, a non-vehicle charging unit 18as described below with respect to FIGS. 7-9. According to embodimentsof the invention, vehicles 4-8 and charging station 16 are configured tocooperate together to share power electronics among the vehicles 4-8 andoptional off-board charging unit 18 to provide a charging current to oneof the vehicles, such as vehicle 6, to augment and increase the chargingcurrent generated by the vehicle alone.

Each vehicle 4-8 includes a plurality of power electronics 20 coupled toa least one energy storage device 22. During operation of vehicle 4-8, acontroller 24 causes a DC voltage from energy storage device 22 to bemodified and delivered to an electromechanical device or motor 26mechanically coupled to one or more driving wheels or axles 28 during amotoring mode of operation. In another embodiment, the DC voltage fromenergy storage device 22 may be modified and delivered to another load(not shown) such as air conditioning compressors, fans, pumps, or otherauxiliary drives.

Vehicles 4-8 may include AC motors 26, and controller 24 is configuredto cause a DC voltage from energy storage device 22 to be inverted to anAC voltage via power electronics 20 for delivery to motor 26. In thisembodiment, vehicles 4-8 may be on-road and off-road vehicles or utilitytrucks, for example. In another embodiment, vehicles 4-8 may include DCmotors 26, and controller 24 is configured to cause a DC voltage fromenergy storage device 22 to be converted to a variable DC voltage viapower electronics 20 for delivery to motor 26 during a motoring mode ofoperation. In this embodiment, vehicles 4-8 may be fork lift trucks,golf cars, or neighborhood electric vehicles, for example.

When a vehicle 4-8 is parked or not in use, it may be desirable to plugthe vehicle into, for example, the utility grid or to a renewable energysource to refresh or recharge energy storage device 22. Accordingly,vehicles 4-8 are coupleable to charging station 16 via a connectionsystem 30 comprising mating contacts 32, 34. Charging station 16includes a power bus 36 configured to supply or provide power to powerelectronics 20 of the vehicle 4-8. In one embodiment, power bus 36 is a3-phase AC power bus such as the utility grid. It is contemplated,however, that power bus 36 may include any number of phases and maysupply or receive AC or DC power.

According to embodiments of the invention, charging station 16 includesa shared DC voltage bus 38 configured to augment and increase thecharging current generated by one of the vehicles coupled to chargingstation 16. Charging station 16 also includes a controller 40 coupled toa plurality of contactor groups 42, 44, 46 for each charging bay 10, 12,14 available at charging station 16. In one embodiment, each contactorgroup 42-46 has a pair of contactors 48, 50 coupled to shared DC voltagebus 38 and a plurality of contactors 52, 54, 56 coupled to power bus 36.Controller 40 is configured to control contactors 48-56 and tocommunicate with each vehicle controller 24 to direct and controlcharging of the vehicles coupled to charging station 16. In oneembodiment, controller 40 is configured to communicate with each vehiclecontroller 24 via power line communications over power bus 36. However,other modes of communication, such as wireless communication orcommunication via a dedicated communication line, are also contemplatedherein.

As illustrated in FIG. 1, vehicles 4-8 are coupled to charging station16. According to the embodiment shown, vehicles 4 and 8 are using theirpower electronics 20 to provide power from power bus 36 to shared DCvoltage bus 38 such that the charging power provided to the energystorage device 22 of vehicle 6 may augmented. That is, while vehicle 6draws power from power bus 36 for conversion into a charging powerprovided to its energy storage device 22, the additional charging powerprovided and controlled by vehicles 4 and 8 is also provided to theenergy storage device 22 via shared DC voltage bus 38, and the energystorage device 22 of vehicle 6 may accordingly be rapidly charged.

In one embodiment, the cost to a vehicle owner for plugging intocharging station 16 and drawing charging power therefrom may vary perunit charge according to a level of charging mode desired. For example,charging station 16 may be configured to allow selection of arapid/sharing charging mode, a non-rapid/non-sharing charging mode, anda non-rapid/sharing charging mode.

In the rapid/sharing charging mode, the vehicle is connected to chargingstation 16 and awaits its turn to rapidly charge its energy storagedevice 22. In this mode, the respective contactors 48, 50 are closedsuch that the vehicle's charging bus may be coupled to shared DC voltagebus 38. While the vehicle is awaiting its turn for rapid charging andafter its turn has been completed, its power electronics 20 are sharedwith other vehicles coupled to charging station 16 via the respectivecontactors 48, 50 to charge another vehicle currently allowed to rapidlycharge its energy storage device 22.

In the non-rapid/non-sharing charging mode, the vehicle is connected tocharging station 16 and begins to charge its energy storage device 22only from the power electronics 20 on-board the vehicle withoutconnection of its energy storage device 22 to the shared DC voltage bus38. That is, in this charging mode, the respective contactors 48, 50remain open, and the vehicle's energy storage device 22 is chargedsolely via the vehicle's on-board power electronics 20.

In the non-rapid/sharing charging mode, the vehicle is connected tocharging station 16, and the respective contactors 48, 50 are closedsuch that the vehicle's charging bus may be coupled to shared DC voltagebus 38. In this charging mode, the vehicle participates in powerelectronics sharing while another vehicle is rapidly charging its energystorage device 22. The vehicle, however, is disconnected from shared DCvoltage bus 38 if no other vehicle is in a rapid charging mode, and thevehicle's power electronics 20 are used to charge the vehicle's energystorage device 22 solely via the vehicle's on-board power electronics20. When another vehicle later enters a rapid charging mode, the vehicleagain participates in power electronics sharing during this time.

According to one embodiment, the rapid/sharing charging mode may resultin the highest cost per charging unit for a vehicle owner/operator, andthe non-rapid/sharing charging mode may result in the least cost percharging unit for a vehicle owner/operator. As such, the vehicleowner/operator may be charged at a premium rate, for example, for theability to rapidly charge the vehicle's energy storage device 22 in therapid/sharing charging mode, while the vehicle owner/operator may becharged at a reduced rate, for example, for sharing the vehicle's powerelectronics 20 in the non-rapid/sharing charging mode. For thenon-rapid/non-sharing charging mode, the vehicle owner/operator may becharged at a rate, for example, between the premium rate and the reducedrate. The decision of which charging mode to select may be made by thevehicle owner/operator based on the need of the energy storage device 22to receive a rapid charge and the comparative costs between the chargingmodes.

FIG. 2 is a schematic diagram of a portion of the charging system 2 ofFIG. 1 according to an embodiment of the invention. FIG. 2 showsexemplary schematics for each vehicle 4, 6. Each vehicle 4, 6 includes atraction system 58 that includes energy storage device 22 and powerelectronics 20. Power electronics 20 include a bi-directional DC-to-ACvoltage inverter 60 coupled to energy storage device 22 via a DC bus 62.In one embodiment, energy storage device 22 is a high-voltage energystorage device and may be a battery, a flywheel system, fuel cell, anultracapacitor, or the like. A DC link filter capacitor 64 is coupledacross DC bus 62 to filter high-frequency currents on DC bus 62. Acontactor 66 coupled to DC bus 62 allows energy storage device 22 to bedecoupled from DC bus 62. Bi-directional DC-to-AC voltage inverter 60 isa voltage converter and includes six half phase modules 68, 70, 72, 74,76, and 78 that are paired to form three phases 80, 82, and 84. Eachphase 80, 82, 84 is coupled to a pair of conductors 86, 88 of DC bus 62.

Motor 26 is coupled to bi-directional DC-to-AC voltage inverter 60. Inone embodiment, motor 26 is a traction motor mechanically coupled to oneor more driving wheels or axles 28 (shown in FIG. 1) or other electricalapparatus including cranes, elevators, or lifts. Electromechanicaldevice 26 includes a plurality of windings 90, 92, and 94 coupled torespective phases 80, 82, 84 of bi-directional DC-to-AC voltage inverter60. Windings 90-94 are also coupled together to form a node 96. Duringthe charging of energy storage device 22 via charging station 16 andafter receiving communication and confirmation of charging mode fromcontroller 40, controller 24 causes a plurality of contactors 98, 100,102 to respectively decouple windings 90-94 from bi-directional DC-to-ACvoltage inverter 60 such that motor 26 remains unpowered.

Controller 24 is coupled to half phase modules 68-78 via a plurality oflines 104. During use of vehicle 4, 6 in a non-charging mode, controller24 applies appropriate control of half phase modules 68-78 and controlsbi-directional DC-to-AC voltage inverter 60 to convert a DC voltage orcurrent on DC bus 62 to an AC voltage or current for supply to windings90-94. Accordingly, the DC voltage or current from energy storage device22 may be converted into an AC voltage or current and delivered to motor26 to drive wheels 28. In other non-vehicle propulsion systems, thedrive wheels 28 may be another type of load (not shown), including apump, fan, winch, crane, elevator, or other motor driven loads. In aregenerative braking mode, electromechanical device 26 may be operatedas a generator to brake wheels 28 or, for non-vehicle propulsionsystems, other types of loads and to provide AC voltage or current tobi-directional DC-to-AC voltage inverter 60 for inversion into a DCvoltage or current onto DC bus 62 that is suitable for recharging energystorage device 22.

Contactors 48, 50 are in the open state prior to coupling vehicles 4, 6to charging station 16. Depending on the communication medium betweencontroller 40 and the controllers 24 of vehicles 4, 6, contactors 52-56may be in the open or closed state. For example, if controller 40 andthe controllers 24 of vehicles 4, 6 are configured to communicate overthe power line, contactors 52-56 may be in the closed state to allowsuch communications when a vehicle 4, 6 is coupled to charging station16. However, if controller 40 and the controllers 24 of vehicles 4, 6are configured to communicate via a different communication mode,contactors 52-56 may be in the open state. Contactors 98-102 are putinto the open state prior to closing contactors 52-56 such that motor 26remains unpowered during connection to charging station 16 as describedabove.

When a vehicle, such as vehicle 6, is plugged into or coupled tocharging station 16, controller 40 establishes communication with thecontroller 24 of vehicle 6 to determine the desired charging mode andother parameters. The other parameters may include, for example, whetherthe DC nominal voltage of energy storage device 22 is within a giventhreshold and within minimum and maximum voltage limits of the chargingstation 16. If the desired charging mode includes sharing powerelectronics and another vehicle is in the rapid charging mode,controller 40 closes contactors 48, 50 and communicates with controller24 of vehicle 6 that its power electronics 20 should convert power frompower bus 36 for providing power to shared DC voltage bus 38. If thedesired charging mode includes rapidly charging the energy storagedevice 22 of vehicle 6, controller 40 communicates with controller 24 ofvehicle 6 when it is possible to close contactor 66 to begin the rapidcharging of the energy storage device 22 of vehicle 6.

The other parameters may also include a status of the energy storagedevice 22 currently being charged. For example, the controller 24 ofvehicle 6 may be configured to monitor energy storage device 22 usingknown algorithms to prevent overcharge, etc. In another embodiment, thecontroller 24 of vehicle 6 may be configured to communicate commandsthrough controller 40 to the controllers 24 of the other vehicles. Thesecommands may be, for example, commands for the other vehicles to startramping the current on shared DC voltage bus 38, to hold the current onshared DC voltage bus 38 at the present value, or to start lowering thecurrent on shared DC voltage bus 38 by a delta amount.

Controller 24 is configured to control half phase modules 68-78 to boostthe voltage of the power supplied thereto from power bus 36 such thatcharging power may be provided to energy storage device 22 or to sharedDC voltage bus 38 that is a voltage greater than that allowable throughsimple full-wave rectification of the power from power bus 36 withoutboosting. Respective pairs of half phase modules 68-70, 72-74, 76-78,together with a plurality of respective inductors 106, 108, 110, formindividual boost converters that operate to boost the current and/orvoltage of the power supplied thereto from power bus 36. In oneembodiment, inductors 106-110 are high frequency inductor componentslocated in charging station 16 and are off board of vehicles 4, 6. Inanother embodiment, inductors 106-110 represent a leakage inductance ofthe line transformer of power bus 36.

When one or more vehicles, such as vehicle 6 and/or vehicle 8, is usedto share its power electronics 20 with the power electronics 20 ofvehicle 6 for the rapid charging of the energy storage device 22 ofvehicle 6, the bi-directional DC-to-AC voltage inverters 60 operateessentially in parallel.

After charging is complete or when a vehicle operator desires to unplugthe vehicle from the charging station 16, controller 40 establisheshandshaking communication with the controller 24 of the vehicle, such asvehicle 6, to confirm that the vehicle is in a non-charging mode andthat the vehicle is disconnected from charging station 16. In oneembodiment, for example, contacts 32, 34 of connection system 30 may bedisengaged only after contactors 48-56 of the respective charging bay10-14 have been opened and after the contacts 32, 34 have been unlocked.An indicator (not shown) on the vehicle, the connection system 30, orthe charging station 16 may indicate a locked/unlocked status of theconnection system 30.

FIG. 3 is a schematic diagram of the charging system shown in FIG. 2according to another embodiment of the invention. In addition to thatshown with respect to FIG. 2, charging station 16 includes a multi-phasetransformer 112, 114 for each charging bay 10, 12 available at chargingstation 16. Multi-phase transformers 112, 114 provide electricalisolation of the power electronics 20 from power bus 36. In addition,the outputs of the bi-directional DC-to-AC voltage inverters 60 viacontactors 48, 50 operate in parallel while the inputs to thebi-directional DC-to-AC voltage inverters 60 via contactors 52-56 areremoved from parallel operation. While wye-delta three-phasetransformers are shown, it is contemplated that other arrangements (suchas a zigzag winding arrangement) could be used to achieve alternativewaveform phase shifting to reduce harmonic currents on the utility.Multi-phase transformers 112, 114 also allow selecting the most desiredAC voltage for feeding the power electronics 20.

Vehicles 4, 6 also include a charge resistor 116 and a charge contactor118. In an embodiment of the invention, charge contactor 118 may beclosed to limit current flowing into energy storage device 22 when itsvoltage is below a predetermined threshold during an initial charge ofenergy storage device 22.

FIG. 4 shows a schematic diagram of a traction system 120 of vehicle 6according to another embodiment of the invention. Elements andcomponents common to traction systems 58 and 120 will be discussedrelative to the same reference numbers as appropriate. In addition tothe components common with traction system 58, traction system 120includes a second energy storage device 122 coupled to DC bus 62 toprovide power to bi-directional DC-to-AC voltage inverter 60 to drivemotor 26 and wheels 28 (shown in FIG. 1). In one embodiment, secondenergy storage device 122 is a low-voltage energy storage device and maybe a battery, a fuel cell, an ultracapacitor, or the like. First energystorage device 22 may be configured to provide a higher power thansecond energy storage device 122 to provide power during, for example,acceleration periods of the vehicle. Second energy storage device 122may be configured to provide a higher energy than first energy storagedevice 22 to provide a longer-lasting power to the vehicle to increase atraveling distance thereof. As illustrated in FIG. 4, in one embodiment,first energy storage device 22 is an ultracapacitor.

A plurality of bi-directional DC-to-DC voltage converters 124, 126, 128are configured to convert one DC voltage into another DC voltage.Bi-directional DC-to-DC voltage converter 124-128 are coupleable tosecond energy storage device 122 via a node 130 coupled to a contactor132 and are coupled to DC bus 62. Each bi-directional DC-to-DC voltageconverter 124-128 includes an inductor 134 coupled to a pair of halfphase modules 136, 138. For illustrative purposes, half phase modules136, 138 are shown to include insulated gate bipolar transistors(IGBTs). However, embodiments of the invention are not limited to IGBTs.Any appropriate electronic switch can be used, such as, for example,metal oxide semiconductor field effect transistors (MOSFETs), SiliconCarbide (SiC) MOSFETs, bipolar junction transistors (BJTs), and metaloxide semiconductor controlled thyristors (MCTs).

Controller 24 is coupled to bi-directional DC-to-DC voltage converters124-128 via lines 104, and energy provided via second energy storagedevice 122 is boosted by control of bi-directional DC-to-DC voltageconverters 124-128 to provide the higher voltage to DC bus 62. Theenergy provided via second energy storage device 122 to DC bus 62 isinverted via bi-directional DC-to-AC voltage inverter 60 and provided tomotor electromechanical device 26. Similarly, energy generated during aregenerative braking mode may also be used to re-charge second energystorage device 122 via bi-directional DC-to-AC voltage inverter 60 andvia bucking control of bi-directional DC-to-DC voltage converters124-128.

As shown in FIG. 4, bi-directional DC-to-AC voltage inverter 60 ofvehicle 6 is not coupled to second energy storage device 122 directly inparallel. Instead, as described above, power provided to DC bus 62 tocharge second energy storage device 122 is controlled via buckingcontrol of bi-directional DC-to-DC voltage converters 124-128. In anembodiment of the invention, the voltage capacity of second energystorage device 122 is lower than a rectified voltage of the voltage onpower bus 36. Accordingly, bi-directional DC-to-AC voltage inverter 60need not boost the voltage on power bus 36 but may be used to simplyrectify the power bus voltage. That is, the switches in half phasemodules 68-78 need not be switched or controlled via controller 24 in acharging operation of second energy storage device 122 using chargingstation 16. While bi-directional DC-to-AC voltage inverter 60 need notboost the voltage on power bus 36, it may nevertheless be controlled todo so. In addition, an isolation or multi-phase transformer, such asmulti-phase transformer 112 shown in FIG. 3, may be used as describedabove with charging station 16 shown in FIG. 4. If switching control ofhalf phase modules 68-78 is not used such that current from power bus 36is not shaped via the switching control, harmonic currents may bereduced by employing various phase shifting arrangements of theisolation transformer to cancel harmonics.

To rapidly charge second energy storage device 122, controllers 24 and40 can cooperate together to close contactors 48, 50 and contactor 132of traction system 120 coupled to second energy storage device 122 suchthat the current from shared DC voltage bus 38 provided from othervehicles or from non-vehicle charging unit 18, for example, may bejoined with charging current provided by bi-directional DC-to-DC voltageconverters 124-128. Controllers 24 and 40 can also cooperate together toclose contactors 48, 50 and to open contactor 132 such that vehicle 6can share its power electronics 20 for rapid charging of the energystorage device of another vehicle coupled to charging station 16.

FIG. 5 shows a schematic diagram of traction system 120 of vehicle 6according to another embodiment of the invention. As shown in FIG. 5,first energy storage device 22 is a high-voltage energy storage devicesuch as a battery, a fuel cell, or the like as described above and has avoltage capacity higher than a rectified voltage of the voltage on powerbus 36. Second energy storage device 122 may be configured, in anembodiment, to have a power limit that does not allow high power rapidcharge as described above with respect to FIG. 4. In this embodiment,charging current supplied through shared DC voltage bus 38 to vehicle 6is directed, via boost control of bi-directional DC-to-DC voltageconverters 124-128, to DC bus 62 of vehicle 6 together with the chargingcurrent provided to DC bus 62 via boost control of phases 80-84 ofbi-directional DC-to-AC voltage inverter 60. The charging current on DCbus 62 is directed to energy storage device 22 through contactor 66 torapidly charge energy storage device 22. In this manner, six channels ofthe traction system 120 may be used to rapidly charge energy storagedevice 22. In one embodiment, charging of second energy storage device122 may be accomplished by opening contactors 48, 50, closing contactor132, and bucking charging current on DC bus 62 supplied thereto byeither energy storage device 22 or by rectification of power from powerbus 36.

FIG. 6 shows a schematic diagram of traction system 120 of FIG. 5according to another embodiment of the invention. A contactor 140 iscoupled to a node 142 coupled between second energy storage device 122and contactor 132. As shown, bi-directional DC-to-DC voltage converter128 is coupled to node 142, while bi-directional DC-to-DC voltageconverters 124, 126 remain coupled to node 130.

In this embodiment, it is possible to charge energy storage device 22via six channels of traction system 120 as described above with respectto FIG. 5. That is, by opening contactor 140 and by closing contactor132, bi-directional DC-to-DC voltage converters 124-128 and phases 80-84of bi-directional DC-to-AC voltage inverter 60 may be controlled in aboosting mode to provide charging current to energy storage device 22via DC bus 62 and contactor 66.

Alternatively, it is possible to charge energy storage device 22 viafive channels of traction system 120 while simultaneously chargingsecond energy storage device 122 via one channel of traction system 120.That is, controller 24 may open contactor 132 and cause bi-directionalDC-to-DC voltage converters 124-126 and phases 80-84 of bi-directionalDC-to-AC voltage inverter 60 in a boosting mode to provide chargingcurrent to DC bus 62. Controller 24 may then close contactor 66 tocontrol rapid charging of energy storage device 22. In addition,controller 24 may also close contactor 140 and control bi-directionalDC-to-DC voltage converter 128 in a bucking mode to charge second energystorage device 122.

FIG. 7 is a schematic diagram of another portion of the charging system2 of FIG. 1 according to an embodiment of the invention. FIG. 7 showsexemplary schematics for vehicle 6 and for non-vehicle charging unit 18.Charging unit 18 includes an AC-to-DC voltage inverter 144 coupleable toshared DC voltage bus 38 via a DC bus 146 and via contactors 48, 50. ADC link filter capacitor 148 is coupled across DC bus 146. AC-to-DCvoltage inverter 144 includes six half phase modules 150, 152, 154, 156,158, and 160 that are paired to form three phases 162, 164, and 166.Each phase 162, 164, 166 is coupled to a pair of conductors 168, 170 ofDC bus 146. A controller 172 is coupled to half phase modules 150-160via a plurality of lines 174 and controls respective pairs of half phasemodules 150-152, 154-156, 158-160, together with a plurality ofrespective inductors 176, 178, 180, to boost the current and/or voltageof the power supplied thereto from power bus 36. In one embodiment,inductors 176-180 are high frequency inductor components located incharging system 16. In another embodiment, inductors 176-180 represent aleakage inductance of the line transformer of power bus 36.

Charging unit 18 may be included in charging system 2 to furtherincrease the power available for rapid charging of a single vehicle. Inaddition, charging unit 18 allows the rapid charging of the energystorage device 22 of vehicle 6 at a higher power levels than areavailable from the on-board power electronics 20 of vehicle 6 even whenno other vehicle is coupled to charging station 16 or when no othervehicle is configured to share its power electronics. Combining theon-board power electronics 20 of vehicle 6 with the power electronics ofcharging unit 18 allows rapid charging of the energy storage device 22of vehicle 6 from a lower cost, lower power rated, off-board chargerversus rapid charging via using exclusively off-board power electronics.For example, if the on-board power electronics 20 of vehicle 6 are ratedat 99 kW and the off-board power electronics of charging unit 18 arerated at 100 kW, then 199 kW of rapid charge power may be provided toenergy storage device 22 of vehicle 6. If two other vehicles, such asvehicles 4 and 8, are also coupled to charging station 16 and configuredto share their power electronics 20 rated at 99 kW each, then 397 kW ofrapid charge power may be provided to energy storage device 22 ofvehicle 6. The power ratings specified in this example are merelyexemplary, and other power ratings are contemplated. For example,charging unit 18 may be designed such that its power electronics arerated higher than 100 kW. The design of the power ratings of chargingunit 18 may be based in part on the complexity and costs of theconstruction of charging system 2.

FIG. 8 is a schematic diagram of charging unit 18 of FIG. 7 according toanother embodiment of the invention. Elements and components common tothe charging units 18 shown in FIGS. 7 and 8 will be discussed relativeto the same reference numbers as appropriate. In addition to thecomponents common with charging unit 18 of FIG. 7, charging unit 18 ofFIG. 8 includes an energy storage device 182 coupleable to a DC bus 184via a contactor 186. Energy storage device 182 is configured to provideadditional power to shared DC voltage bus 38. In one embodiment, energystorage device 182 is a high-voltage energy storage device and may be abattery, a flywheel system, fuel cell, an ultracapacitor, or the like.

A plurality of bi-directional DC-to-DC voltage converters 188, 190, 192are configured to convert one DC voltage into another DC voltage.Bi-directional DC-to-DC voltage converter 188-192 are coupled to DC bus184 and are coupleable to energy storage device 182 via contactor 186.Each bi-directional DC-to-DC voltage converter 188-192 includes aninductor 194 coupled to a pair of half phase modules 196, 198. Forillustrative purposes, half phase modules 196, 198 are shown to includeinsulated gate bipolar transistors (IGBTs). However, embodiments of theinvention are not limited to IGBTs. Any appropriate electronic switchcan be used, such as, for example, metal oxide semiconductor fieldeffect transistors (MOSFETs), Silicon Carbide (SiC) MOSFETs, bipolarjunction transistors (BJTs), and metal oxide semiconductor controlledthyristors (MCTs). Bi-directional DC-to-DC voltage converter 188-192 arecoupleable to contactor 50 via a contactor 200, and DC bus 146 iscoupleable to contactor 50 via a contactor 202. A contactor 204 isconfigured to couple DC bus 146 to DC bus 184. In addition, controller172 is coupled to bi-directional DC-to-DC voltage converters 188-192 vialines 174.

Energy storage device 182 allows the rapid charging of a vehicle energystorage device, such as energy storage device 22 of vehicle 6, at ahigher power levels than are available from AC-to-DC voltage inverter144 alone. During a vehicle charging operation using both AC-to-DCvoltage inverter 144 and energy storage device 182, controller 172causes contactor 204 to open and causes contactors 186, 200, and 202 toclose. Controller 172 then controls respective pairs of half phasemodules 150-152, 154-156, 158-160, together with inductors 176-180 toboost the current and/or voltage of the power supplied thereto frompower bus 36 and to deliver the boosted current/voltage to shared DCvoltage bus 38. In addition, controller 172 controls bi-directionalDC-to-DC voltage converters 188-192 to buck a voltage from energystorage device 182 and to deliver the boosted current to shared DCvoltage bus 38. DC bus 146 and DC bus 184 may be independentlycontrolled to provide energy to shared DC voltage bus 38.

Energy storage device 182 may be charged by closing contactors 186, 204and by opening contactors 200, 202. In this manner, controller 172controls respective pairs of half phase modules 150-152, 154-156,158-160, together with inductors 176-180 to boost the voltage of thepower supplied thereto from power bus 36 and to deliver the boostedvoltage to energy storage device 182. In an embodiment of the invention,the charging of energy storage device 182 may be performed duringperiods of low demand or low cost, for example, for the power on powerbus 36. Energy storage device 182 may be used to augment the powerprovided to shared DC voltage bus 38 via AC-to-DC voltage inverter 144during periods of high demand or high cost, for example, such as duringhigh temperature days.

FIG. 9 is a schematic diagram of charging unit 18 of FIG. 8 according toanother embodiment of the invention. Elements and components common tothe charging units 18 shown in FIGS. 7-9 will be discussed relative tothe same reference numbers as appropriate. In addition to the componentscommon with charging unit 18 of FIGS. 7 and 8, charging unit 18 of FIG.9 includes a second energy storage device 206 coupleable tobi-directional DC-to-DC voltage converter 192 via a contactor 208. Inone embodiment, second energy storage device 206 is a low-voltage energystorage device and may be a battery, a fuel cell, an ultracapacitor, orthe like. Energy storage device 182 may be configured to provide ahigher power than second energy storage device 206. Second energystorage device 206 may be configured to provide a higher energy thanenergy storage device 182. Bi-directional DC-to-DC voltage converters188, 190 are coupleable to contactor 50 via a contactor 210.

Second energy storage device 206 allows the rapid charging of a vehicleenergy storage device, such as energy storage device 22 of vehicle 6, ata higher power levels than are available from AC-to-DC voltage inverter144 and energy storage device 182. During a vehicle charging operationusing AC-to-DC voltage inverter 144, energy storage device 182, andsecond energy storage device 206, controller 172 causes contactor 204 toopen and causes contactors 186, 202, 208, and 210 to close. Controller172 then controls respective pairs of half phase modules 150-152,154-156, 158-160, together with inductors 176-180 to boost the voltageof the power supplied thereto from power bus 36 and to deliver theboosted voltage to shared DC voltage bus 38. Controller 172 controlsbi-directional DC-to-DC voltage converter 192 to boost a voltage fromsecond energy storage device 206 and to deliver the boosted voltage toDC bus 184. Controller 172 also controls bi-directional DC-to-DC voltageconverters 188-190 to buck a voltage from energy storage device 182 andthe boosted voltage from second energy storage device 206 and to deliverthe boosted current/voltage to shared DC voltage bus 38. DC bus 146 andDC bus 184 may be independently controlled to provide energy to sharedDC voltage bus 38. In addition, contactors 186, 208 and bi-directionalDC-to-DC voltage converters 188-190 may be independently controlled toconvert energy from either energy storage device 182 or second energystorage device 206 for delivery to shared DC voltage bus 38.

Second energy storage device 206 may be charged by closing contactors204, 208 and by opening contactors 186, 202, 210. In this manner,controller 172 controls respective pairs of half phase modules 150-152,154-156, 158-160, together with inductors 176-180 to boost the currentand/or voltage of the power supplied thereto from power bus 36 and todeliver the boosted voltage to DC bus 184. From DC bus 184,current/voltage is provided to second energy storage device 206 viabucking control of bi-directional DC-to-DC voltage converter 192. Inanother embodiment of the invention, the charging of energy storagedevice 182 may be performed during periods of low demand or low cost,for example, for the power on power bus 36. Energy storage device 182may be used to augment the power provided to shared DC voltage bus 38via AC-to-DC voltage inverter 144 during periods of high demand or highcost, for example, such as during high temperature days. Controller 172may open contactors 202, 204, 210 and close contactors 186 208 andcontrol bi-directional DC-to-DC voltage converter 192 to buck energyprovided to DC bus 184 from energy storage device 182.

FIG. 10 is a schematic block diagram of charging system 2 according toanother embodiment of the invention. As shown in FIG. 10, contactorgroups 42, 44 are positioned on board vehicles 4, 6. According to anembodiment, controllers 24 of vehicles 4, 6 are configured to controlcontactors 48-56 and to communicate with each other via power linecommunications over power bus 36 or via other modes of communication asdescribed above. In this manner, charging station 16 only providesconnections to power bus 36 and shared DC voltage bus 38 for charging,rapid charging, and sharing power electronics 20 between vehicles 4, 6.Controllers 24 of vehicles 4, 6 are configured to communicate with eachother regarding the rapid charging and power electronic sharingtherebetween. While only vehicles 4 and 6 are illustrated in FIG. 10, itis contemplated that more than two vehicles could be configured andcoupled together in the manner shown.

FIG. 10 also shows an embodiment of connection system 30 coupled tovehicles 4, 6. In this manner, a cord or tether 212 coupled to matingcontact 34 and coupling each vehicle 4, 6 to charging station 16 may beextend from and be supplied by the charging station 16 rather than beingprovided on board vehicles 4, 6 to reduce a cost and/or weight ofvehicles 4, 6.

Embodiments of the invention thus use components such as inverters andconverters already on-board a traction control system to charge one ormore energy storage devices of the traction control system and toprovide charging current to other traction control systems in a sharingmode. In this manner, these components may be used for the dual purposesof motoring and recharging the energy storage devices. Using theon-board components of one or more vehicles to rapidly charge the energystorage device of another vehicle allows for off-board charging stationsto have a simple, low cost design. In addition, charging may beorganized in a cost effective pricing schedule such that chargingbecomes more cost effective when the choice of sharing the powerelectronics of the vehicle for other vehicles is selected. Rapid, fastcharging of the on-board energy storage devices may be thus accomplishedthrough vehicle power electronics sharing such that off-board chargingstations may be constructed and operated in a more cost effective mannerthan an off-board charging station built to provide high levels ofcurrent and power for rapid charging alone.

A technical contribution for the disclosed apparatus is that it providesfor a controller implemented technique for rapidly charging one electricdrive system using shared power electronics of one or more additionalelectric drive systems.

According to one embodiment of the invention, an apparatus comprises apower electronic energy conversion system comprising a first energystorage device configured to store DC energy and a first voltageconverter configured to convert a stored voltage from the first energystorage device into a first voltage configured to drive anelectromechanical device. The first voltage converter is also configuredto convert a second voltage from a remote power supply into a firstcharging voltage configured to charge the first energy storage device.The apparatus also includes a first controller configured to control thefirst voltage converter to convert the second voltage into the firstcharging voltage and to provide the first charging voltage to the firstenergy storage device during a charging mode of operation andcommunicate with a second controller located remotely from the powerelectronic energy conversion system to cause a second charging voltageto be provided to the first energy storage device during the chargingmode of operation to rapidly charge the first energy storage device.

In accordance with another embodiment of the invention, a methodcomprises coupling a first energy storage device to a first voltageconverter, wherein the first energy storage device is configured tostore electrical energy and wherein the first voltage converter isconfigured to convert a stored voltage from the first energy storagedevice into a first voltage configured to drive a motor and to convert asecond voltage from a first remote power supply into a first chargingvoltage configured to charge the first energy storage device. The methodalso comprises coupling a first controller to the first voltageconverter and configuring the first controller to cause the firstvoltage converter to convert the second voltage into the first chargingvoltage and to provide the first charging voltage to the first energystorage device during a rapid charging mode of operation. The methodfurther comprises configuring the first controller to cause a secondcharging voltage from a second remote power supply to be provided to thefirst energy storage device during the rapid charging mode of operationto rapidly charge the first energy storage device.

In accordance with yet another embodiment of the invention, a systemcomprises a first power bus, a second power bus, and a first vehicle.The first vehicle comprises a first energy storage device configured tostore DC energy, a first motor and a first voltage converter configuredto convert a stored voltage from the first energy storage device into amotoring voltage configured to drive the first motor and to convert afirst voltage from the first power bus into a first charging voltageconfigured to charge the first energy storage device. The first vehiclealso comprises a first controller configured to control the firstvoltage converter to convert the first voltage into the first chargingvoltage and to provide the first charging voltage to the first energystorage device. The system also comprises a first energy conversionsystem located remotely from the first vehicle and comprising a secondvoltage converter configured to convert the first voltage from the firstpower bus into a second charging voltage configured to charge the firstenergy storage device of the first vehicle. The first energy conversionsystem further comprises a second controller configured to control thesecond voltage converter to convert the first voltage into the secondcharging voltage and to provide the second charging voltage to thesecond power bus and communicate with the first controller to cause thesecond charging voltage to be provided from the second power bus to thefirst energy storage device to rapidly charge the first energy storagedevice.

While the invention has been described in detail in connection with onlya limited number of embodiments, it should be readily understood thatthe invention is not limited to such disclosed embodiments. Rather, theinvention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention. Additionally, while various embodiments of the invention havebeen described, it is to be understood that aspects of the invention mayinclude only some of the described embodiments. Accordingly, theinvention is not to be seen as limited by the foregoing description, butis only limited by the scope of the appended claims.

What is claimed is:
 1. A vehicle charging system comprising: an energy storage device; a first DC/DC converter coupleable via a first switching device to the energy storage device; power electronics comprising a second DC/DC converter for a traction drive system coupleable to the energy storage device via a second switching device, the traction drive system comprising an inverter coupled to a traction motor; wherein the second switching device is configured to selectively decouple the second DC/DC converter from the energy storage device during a period when the energy storage device is coupled to the first DC/DC converter via the first switching device to be charged from an external charging source.
 2. The vehicle charging system of claim 1, further comprising a controller configured to selectively open the second switching device to electrically decouple the second DC/DC converter from the energy storage device during a period when the first switching device is closed to electrically couple the first DC/DC converter to the energy storage device to charge the energy storage device from the external charging source.
 3. The vehicle charging system of claim 1, further comprising a second energy storage device.
 4. The vehicle charging system of claim 3, further comprising an auxiliary drive configured to receive a modified voltage from the second energy storage device.
 5. The vehicle charging system of claim 3, wherein the second energy storage device is coupleable to the traction drive system via a third switching device.
 6. The vehicle charging system of claim 1, further comprising an axle coupled to the traction motor, the axle including one or more drive wheels.
 7. A vehicle charging system comprising: a first energy storage device; a second energy storage device; a first DC/DC converter coupleable to the first energy storage device; an auxiliary drive coupleable to the second energy storage device; power electronics comprising a second DC/DC converter for a traction drive system comprising an inverter coupled to a traction motor; and a plurality of switching devices configured to selectively couple the first energy storage device to the first DC/DC converter, couple the second energy storage device to the second DC/DC converter, and decouple the second DC/DC converter from the first energy storage device during a period when the first and second energy storage devices are being charged from an external charging source, the plurality of switching devices comprising: a first switching device coupled between the first DC/DC converter and the first energy storage device; a second switching device coupled between the second DC/DC converter and the second energy storage device; and a third switching device coupled between the second DC/DC converter and the first energy storage device.
 8. The vehicle charging system of claim 7, wherein the first energy storage device comprises a first battery and the second energy storage device comprises a second battery.
 9. The vehicle charging system of claim 8, wherein the first battery has a lower voltage than the second battery.
 10. The vehicle charging system of claim 7, wherein the auxiliary drive comprises an air-conditioning compressor.
 11. The vehicle charging system of claim 7, wherein the external charging source comprises an AC source.
 12. A vehicle charging system comprising: an energy storage device; a first DC/DC converter coupleable to the energy storage device, the first DC/DC converter being configured to operate in a bucking mode; power electronics comprising a second DC/DC converter for a traction drive system comprising an inverter coupled to a motor/generator, the second DC/DC converter being configured to operate in a boosting mode and a bucking mode; a first switching device coupled between the first DC/DC converter and the energy storage device; and a second switching device coupled between the second DC/DC converter and the energy storage device, the second switching device being configured to selectively decouple the second DC/DC converter from the energy storage device during a period when the first switching device couples the first DC/DC converter to the energy storage device to charge the energy storage device from an external charging source.
 13. The vehicle charging system of claim 12, further comprising an axle coupled to the motor/generator, the axle including one or more drive wheels.
 14. The vehicle charging system of claim 13, wherein the motor/generator operates as a generator during a regenerative braking mode.
 15. The vehicle charging system of claim 14, wherein the motor/generator charges the energy storage device when operating as a generator.
 16. The vehicle charging system of claim 1, wherein the first DC/DC converter is configured to operate in a bucking mode.
 17. The vehicle charging system of claim 1, wherein the second DC/DC converter is configured to operate in a boosting mode and a bucking mode.
 18. The vehicle charging system of claim 1, wherein: the first DC/DC converter is configured to operate in a bucking mode; and the second DC/DC converter is configured to operate in a boosting mode and a bucking mode.
 19. The vehicle charging system of claim 7, further comprising a controller configured to selectively open the third switching device to decouple the second DC/DC converter from the first energy storage device during a period when the first switching device and second switching device are closed to couple the first DC/DC converter to the first energy storage device and the second DC/DC converter to the second energy storage device, respectively, to charge the first and second energy storage devices from the external charging source.
 20. The vehicle charging system of claim 12, further comprising a controller configured to selectively open the second switching device to decouple the second DC/DC converter from the energy storage device during a period when the first switching device is closed to couple the first DC/DC converter to the energy storage device to charge the energy storage device from the external charging source. 